Binary Arithmetic (Addition, Shifts)

Once you understand binary numbers, you need to be able to perform arithmetic operations on them. This lesson covers binary addition and binary shifts, both of which are required for the GCSE Computer Science exam.

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Binary Addition

Binary addition follows rules similar to denary addition, but with only two digits (0 and 1). The key rules are:

Addition	Result	Carry
0 + 0	0	0
0 + 1	1	0
1 + 0	1	0
1 + 1	0	1 (carry 1 to the next column)
1 + 1 + 1	1	1 (carry 1 to the next column)

The most important rule to remember is: 1 + 1 = 10 in binary (just as 9 + 1 = 10 in denary — you write 0 and carry 1).

Worked Example 1: Add 01001010 + 00110101